Cat scratch disease (CSD) has been the subject of considerable clinical and microbiologic interest for many years. An estimated 7,000 cases of cat scratch disease occur each year in the United States. Due to difficulty in diagnosing CSD and its potentially confusing clinical similarity with other disease syndromes, the number of actual cases of CSD in the United States may be closer to 70,000 per year. CSD is described as a subacute regional lymphadenitis temporally associated with the scratch or bite of a cat, and it occasionally results in meningoencephalitis.
Diagnosis of CSD has been a problem because the etiologic agent of the disease has not been previously identified. An unidentified bacillus has been visualized in biopsies from patients with CSD using Warthin-Starry stain but has resisted identification because of difficulties in obtaining an isolated culture. The etiologic agent of CSD has recently been proposed to be xe2x80x9cAfipia felisxe2x80x9d (7). Despite these efforts, it has not been possible thus far to isolate or otherwise associate this agent with most persons suffering from cat scratch disease.
A clinically related disease, bacillary angiomatosis (BA), is a condition characterized by multiple tumors or swelling due to proliferation of the blood vessels. BA is often found in association with an immunocompromised condition, particularly HIV infection. An unidentified bacillus has been visualized in the angiomatous tissues using Warthin-Starry stain (28). DNA extracted from the angiomatous tissues was shown to contain a fragment of 16S rRNA gene related to, but not identical to, the 16S rRNA gene of Rochalimaea quintana. This DNA was not obtained from a pure culture of the organism (28). These investigators were unable to isolate an infectious organism from patient tissues and, therefore, were unable to clearly associate the DNA sequences observed in tissues with an identifiable disease-causing organism. Neither the organism seen in these tissues nor the actual causative agent of the disease was identifiable.
Thus, despite intensive research and widespread effects of the diseases, the etiologic agent(s) of both CSD and BA have evaded identification. This invention describes the identification of an organism, named R. henselae herein, which is causative of both diseases.
R. quintana has been associated with varied clinical syndromes including persistent fever with bacteremia in normal and immunosuppressed individuals (18, 23, 30, 34). Despite the association of R. quintana with disease, R. quintana, has not been firmly linked to CSD. Given the controversy surrounding the etiology of CSD and the association R. quintana with human disease, there exists a need for a method of directly detecting each of these organisms in lymph node tissue from CSD patients.
The invention meets this need by providing a nucleic acid based method of detecting R. quintana infection in a subject. The isolated nucleic acid sequences of the present invention allow primers and probes to be readily designed for such a nucleic acid based detection system.
A need also exists to rapidly identify the presence of infection of a patient by R. henselae. Rapid and efficient determination of such infections will aid in the diagnosis of the previously ambiguous symptoms associated with infection by R. henselae and therefore facilitate the evaluation of a proper course of treatment.
The present invention meets this need by providing purified antigenic polypeptides necessary for detecting the presence of R. henselae antibodies circulating in the serum of patients presently, or previously infected with R. henselae. These same purified antigenic polypeptides can be used to produce antibodies which themselves may be utilized in a method to detect the presence of R. henselae antigen present in a subject, and therefore determine whether a subject is currently, or has previously been infected with R. henselae. 
The present invention relates to a method of diagnosing cat scratch disease and a method of diagnosing bacillary angiomatosis in a subject by detecting the presence of Rochalimaea henselae or an immunogenically specific determinant thereof in the subject. Also provided by the present invention is a method of diagnosing cat scratch disease and a method of diagnosing bacillary angiomatosis in a subject by detecting the presence of antibodies in a subject which bind to antigenic determinants of R. henselae. 
The present invention also provides isolated nucleic acids encoding immunogenic polypeptides of R. henselae. 
Vectors are also provided comprising the nucleic acids of the present invention. The vectors can be used in a host expression system to produce antigenic polypeptides reagents for diagnostic and prophylactic applications.
The present invention further relates to a method of diagnosing Rochalimaea quintana infection in a subject by detecting the presence of a nucleic acid specific to Rochalimaea quintana in a sample from the subject.